Baseball and softball bats have been in use for many years. These bats typically include a handle, a barrel, and a tapered section joining the handle to the barrel. The outer shell of these bats is generally formed with aluminum or another suitable metal or composite construction.
Barrel construction is particularly important in modern bat design. Barrels having a single-wall construction, and more recently, a multi-wall construction, have been developed. Modern bats typically include a hollow interior, such that the bats are relatively lightweight and allow a ball player to generate substantial xe2x80x9cbat speedxe2x80x9d or xe2x80x9cswing speed.xe2x80x9d
Single-wall barrels generally include a single tubular spring within the barrel. Multi-wall barrels typically include two or more tubular springs, or similar structures, that may be of the same or different material composition, within the barrel. The tubular springs in these multi-wall bats are either in contact with one another, such that they form friction joints, are bonded to one another with weld or bonding adhesive, or are separated from one another forming frictionless joints. If the tubular springs are bonded using a structural adhesive, or other structural bonding material, the barrel is essentially a single-wall construction. U.S. Pat. No. 5,364,095, the disclosure of which is herein incorporated by reference, describes a variety of bats having multi-walled barrel constructions.
It is generally desirable to have a bat barrel that is durable, while also exhibiting optimal performance characteristics. Hollow bats typically exhibit a phenomenon known as the xe2x80x9ctrampoline effect,xe2x80x9d which essentially refers to the rebound velocity of a ball leaving the bat barrel as a result of flexing of the barrel wall(s). Thus, it is desirable to construct a bat having a high xe2x80x9ctrampoline effect,xe2x80x9d so that the bat may provide a high rebound velocity to a pitched ball upon contact.
The xe2x80x9ctrampoline effectxe2x80x9d is a direct result of the compression and resulting strain recovery of the barrel. During this process of barrel compression and decompression, energy is transferred to the ball resulting in an effective coefficient of restitution (COR) of the barrel, which is the ratio of the post impact ball velocity to the incident ball velocity (COR=Vpost impact/Vincident). In other words, the xe2x80x9ctrampoline effectxe2x80x9d of the bat improves as the COR of the bat barrel increases.
Multi-walled bats were developed in an effort to increase the amount of acceptable barrel deflection beyond that which is possible in typical single-wall designs. These multi-walled constructions generally provide added deflection without increasing stress beyond the material limits of the barrel materials. Accordingly, multi-walled designs are often preferred to single-wall designs, since they typically produce a better xe2x80x9ctrampoline effect.xe2x80x9d
In general, as the wall thickness or barrel stiffness is increased in a bat barrel, the COR decreases. It is important to maintain a sufficient wall thickness, however, because the durability of the bat typically decreases if the wall is too thin. Thus, if the barrel wall(s) are too thin, the barrel may be subject to denting, in the case of metal bats, or to progressive material failure, in the case of composite bats. As a result, the performance and lifetime of the bat may be reduced if the barrel wall(s) are not thick enough.
In the case of composite bats, moreover, the bat barrels are generally characterized by a very high resin content. This high resin content often limits the elastic properties of the bat barrel. Thus, although these bats have performed relatively well, the xe2x80x9ctrampoline effectxe2x80x9d that they exhibit is generally limited by the high resin content in the bat barrels. Thus, there exists a significant design challenge to construct a bat that exhibits significant xe2x80x9ctrampoline effectxe2x80x9d in conjunction with high durability.
The invention is directed to a ball bat having an interface section having one or more layers of non-resin-impregnated fabric sandwiched between a plurality of resin-impregnated layers in a wall of the bat barrel, and a method of making the same.
In a first aspect, a ball bat includes a barrel, a handle, and a tapered section joining the barrel to the handle. The barrel has an outer wall including a substantially cylindrical outer layer, a substantially cylindrical inner layer, and an interface section located between and integral with the outer layer and the inner layer. The interface section includes one or more layers of fabric sandwiched between a plurality of resin-impregnated composite plies, wherein the layer of fabric includes resin that flowed from the plurality of resin-impregnated composite plies during curing of the bat.
In another aspect, a method of constructing a ball bat includes the steps of placing a substantially cylindrical layer of substantially dry fabric between a plurality of resin-impregnated layers to form a substantially cylindrical interface section. The interface section is then placed between a plurality of substantially cylindrical wall sections that each include one or more composite plies. Heat and pressure are then applied to the interface section and the composite plies to induce a flow of resin from the resin-impregnated layers into the fabric layer, and to form an integral bat barrel made up of the wall sections and the interface section.
In another aspect, a method of constructing a ball bat includes the steps of rolling an inner wall section onto a substantially cylindrical mandrel, rolling a bond inhibiting layer onto the inner wall section, and rolling an inner layer of an outer wall section onto the bond inhibiting layer. A first resin-impregnated reinforcement layer is then rolled onto the inner layer of the outer wall section, after which a substantially dry layer of fabric is rolled onto the first resin-impregnated reinforcement layer. Next, a second resin-impregnated reinforcement layer is rolled onto the fabric layer, and an outer layer of the outer wall section is rolled onto the second resin-impregnated reinforcement layer. Heat and pressure are then applied to the layers to induce a flow of resin from the first and second resin-impregnated reinforcement layers into the fabric layer, and to form an integral bat barrel.
In another aspect, a ball bat includes a barrel, a handle, and a tapered section joining the barrel to the handle. The barrel includes a substantially cylindrical outer wall. A substantially cylindrical interface section, including one or more layers of previously non-resin-impregnated fabric sandwiched between a plurality of resin-impregnated layers, is located in the outer wall of the barrel. The layer of fabric includes resin that flowed from the plurality of resin-impregnated layers during curing of the bat.
Further embodiments, including modifications, variations, and enhancements of the invention, will become apparent. The invention resides as well in subcombinations of the features shown and described.